SAN FRANCISCO – The evacuation of more than 300 people aboard the Asiana Airlines jetliner that crash-landed in San Francisco did not begin until 90 seconds after the aircraft came to rest and only when fire was spotted by a flight attendant, federal investigators said Wednesday.
Getting everyone out of the wide-body Boeing 777 late Saturday morning also was complicated by two escape slides that inflated in the cabin, pinning down two crew members, as the plane careened down Runway 28L.
Based on interviews with six of 12 flight attendants, Deborah Hersman, chairwoman of the National Transportation Safety Board, said at a news briefing that the pilots did not order the evacuation because they wanted to contact air traffic control after the heavily damaged jetliner came to a halt.
Part of the NTSB investigation, she said, will explore why it took so long to initiate the removal of the passengers and what caused the escape slides to inflate prematurely during the crash that killed two people and injured 182.
“We don’t know what the pilots were thinking,” Hersman said. “We need to know what they knew and when, what their procedures were and whether the evacuation took place in an effective manner.”
Federal investigators determined that no fire reached the cabin while the passengers were inside. According to the NTSB, crew members fought the spreading blaze with extinguishers before firefighting units arrived.
Asked whether delays in evacuations occur after crashes, Hersman said flight crews sometimes do not evacuate passengers right away. “Fire is serious,” she added. “When it was seen, the evacuation was started.”
During the briefing, Hersman outlined other aspects of the ongoing investigation, including a deeper analysis of the plane’s automated flight systems to determine how they interacted, whether the pilots used them properly or if they malfunctioned during the landing.
Noting that the Boeing 777 has some of the most sophisticated automation in the sky, Hersman said the systems, such as the auto-throttles, have many settings and can be coupled with one another. Investigators found that in the 2 1/2 minutes before the crash, multiple auto-throttle modes and multiple autopilot modes had been set.
“What was the final mode the airplane was in?” Hersman asked. “We still need to validate the data. We need to make sure how the devices were set and what the pilots understood the modes to be.”
Along with the automated systems, Hersman said investigators will look at the relationship of the pilots during the landing to see if there was a so-called “authority gradient” that might have affected one pilot’s willingness to tell another pilot what to do or to challenge what he was doing.
The plane was flying too low and too slowly in its approach, and investigators suspect the pilots had difficulty maintaining proper air speed for landing.
The NTSB also will explore claims by one of the pilots that he was blinded by a flash of light during the approach.